Nuchal-type fibroma (NTF) usually arises in the posterior aspect of the neck. Previously published reports describe only 11 cases and provide limited clinicopathologic information.
Nuchal-type fibroma (NTF) usually arises in the posterior aspect of the neck. Previously published reports describe only 11 cases and provide limited clinicopathologic information.
Fifty-two examples of NTF from 50 patients were analyzed from the files of the Soft Tissue Registries of the Armed Forces Institute of Pathology in Washington, DC, and the Faculty Hospital in Pilsen, Czech Republic.
The age of the patients ranged from 3 to 74 years (mean, 40 years). There were 41 males and 9 females. Thirty-six NTFs were located in the posterior neck region and 16 were from extranuchal sites. Two patients had had lesions excised from both a nuchal and an extranuchal location. The mean greatest tumor dimension was 3.2 cm. Microscopically, all examples had a superficial (subcutaneous and sometimes dermal) component and consisted of paucicellular, thick bundles of lobulated collagen fibers with inconspicuous fibroblasts. Entrapped adipose tissue and traumatic neuromalike nerve proliferations were typically present. Skeletal muscle infiltration was also seen in a minority of cases. Eleven of 25 patients (44%) for whom clinical information was available reportedly had diabetes. Gardner's syndrome was documented in one patient and was possibly present in two additional individuals. During follow-up, five patients had local recurrences, but none of the recurrences were destructive and all were ultimately controlled by local reexcision.
NTF is a rare, tumorlike accumulation of collagen that often affects the posterior neck region but can also occur in a number of other sites. The process has a strong association with diabetes and also appears to be linked to Gardner's syndrome. Local recurrence probably reflects the persistence of local or systemic factors related to its pathogenesis. Cancer 1999;85:156–63. © 1999 American Cancer Society.
Nuchal-type fibroma (NTF) is a rare, tumorlike proliferation originally described by Enzinger and Weiss.1 This process chiefly occurs in the nuchal and interscapular regions of patients between ages 25 and 60 years. It consists of broad bundles of collagen with only a few interspersed fibroblasts. The lesion is benign but has the potential for recurrence.1 Only rare case reports and one clinicopathologic series of nine cases have thus far been published.2, 3 Involvement of an extranuchal site has been reported on one previous occasion.4 We describe the clinicopathologic features of 52 cases of nuchal-type fibroma and demonstrate an association with diabetes and, to a lesser extent, Gardner's syndrome.
The records of the Soft Tissue Registries of the Armed Forces Institute of Pathology in Washington, DC, and the Faculty Hospital in Pilsen, Czech Republic, were reviewed for surgical specimens diagnosed as fibromas involving nuchal and extranuchal sites. All hematoxylin and eosin–stained histologic sections were reviewed, and 52 cases corresponding to nuchal-type fibromas1 were identified among approximately 1000 fibromas, including fibromas of tendon sheath; collagenous fibromas; calcifying aponeurotic fibromas; and fibromas, not otherwise specified. Normal tissue from the nuchal region of 10 randomly selected patients was also studied for comparative purposes.
Immunohistochemical studies were performed on formalin fixed, paraffin embedded tissue from 10 cases of NTF. Sections 5 μm thick were placed on slides coated with 3-aminopropyltriethoxy-silane (Sigma, St. Louis, MO). Microwave-based epitope retrieval in 10 mM citrate buffer (pH 6.0) was used prior to the immunostaining procedure. The immunohistochemical reaction was visualized using the supersensitive streptavidin-biotin-peroxidase complex (BioGenex, San Ramon, CA). The color was developed with diaminobenzidine supplemented with hydrogen peroxide. The sections were lightly counterstained with Mayer's hematoxylin. The primary antibodies and pretreatments are listed in Table 1.
|S-100 protein||SABC||Polyclonal||Dakopatts, Glostrup, Denmark|
|α-Smooth muscle actin||SABC||1A4||Sigma, St. Louis, MO|
|Muscle specific actin||SABC||HHF-35||Dakopatts|
The Soft Tissue archives of the Armed Forces Institute of Pathology and the Faculty Hospital yielded 37 and 13 patients, respectively, who had NTF. There were 41 males (82%) and 9 females (18%). Two individuals had two lesions each. The ages of patients ranged from 3 to 68 years (mean, 40 years) (Fig. 1). Thirty-six lesions were located in the nuchal region and 16 affected extranuchal sites. The NTFs in extranuchal locations most often involved the back or scapular region (6 cases), shoulder (3 cases), and face (3 cases). However, other sites of involvement were the left forearm, anterior neck, knee, and truncal region (1 case each). Two patients with extranuchal NTF also had a separate lesion involving the nuchal region. The patients typically presented with a history of a superficial mass of long duration. Although the surgeons often described the lesions as subcutaneous in location, some examples were noted to extend into deep soft tissue, and on two occasions the periosteum of the skull was reported to be involved.
A high proportion of the patients, 11 of 25 (44%) with clinical information, were reported to have diabetes. One patient with a typical nuchal-type fibroma, a man age 35 years, had Gardner's syndrome. He had known colonic adenomatosis, and his father and an uncle had died of colonic carcinoma. The patient also had multiple skin lesions on the face, one of which was histologically verified as an epidermal inclusion cyst. In addition, two other patients with NTFs had possible Gardner's syndrome. One of these, a male age 19 years with an NTF in the temporal region, had a family history of colonic adenomatosis (uncle), 2 separate large extraabdominal desmoids involving both thighs (15 cm and 14 cm in greatest dimension), and a histologically verified epidermal inclusion cyst in the left ankle. The other patient, a girl age 9 years, had an NTF of 2.5 cm in the anterior aspect of the neck and 2 separate extraabdominal desmoids in the head and neck region.
Macroscopically, NTFs were poorly circumscribed masses with a hard consistency and off-white color. The mean greatest tumor dimension was 3.2 cm (range, 1–6 cm).
Microscopically, the process was paucicellular and composed of thick, haphazardly arranged collagen fibers (Figs. 2,3). In the central parts of the lesions, the collagen bundles often intersected and had a vaguely lobular architecture. In small or recurrent examples with scarring, the lobulation was less conspicuous. The process was predominantly located in the subcutis. However, in instances in which skin was part of the resection specimen, the dermis was often involved; and in most of 15 cases with “deep” clinical extension, there was infiltration and entrapment of the underlying skeletal muscle (Fig. 4).
The sparsely scattered fibroblasts that were present between the collagen fibers had a similar appearance in all cases. They had scant cytoplasm and elongated, twisted, and tapered nuclei with a single inconspicuous nucleolus. Entrapped islands of adipose tissue were seen in most cases (Fig. 5). In 47 of the 52 cases, the NTFs contained entrapped peripheral nerve twigs, sometimes exhibiting a splayed appearance similar to that of a traumatic neuroma (Fig. 6). In 15 cases, the lesions contained enlarged peripheral nerves with perineurial fibrosis similar to that seen in a Morton's neuroma. A delicate network of elastic fibers was often observed between the collagen fibers (Fig. 7). Scant numbers of lymphocytes were present in a minority of cases, but inflammatory features were never prominent. The NTFs in extranuchal sites were morphologically indistinguishable from the examples involving the nuchal region.
Histologic examination of normal tissue from the nuchal region showed thick collagen fibers in the deep dermis reminiscent of those seen in NTF. However, only the NTFs showed lobulation of the collagen fibers, encasement of adnexal structures, and extensive involvement of the subcutis, resulting in a mass effect. Also, neuromalike proliferations of the peripheral nerves were not seen in any of the normal tissue specimens.
Immunohistochemically, the intralesional fibroblastlike cells were consistently positive for vimentin, but they were negative for actin, desmin, S-100 protein, glial fibrillary acidic protein, and epithelial membrane antigen. The proliferating neural elements were S-100 protein positive.
Of the 25 patients with follow-up information, 3 developed 1 recurrence, 1 had 2 recurrences, and another had 3 recurrences. None of the recurrences caused significant functional compromise, and all were eventually successfully managed with local reexcision.
Enzinger and Weiss first described NTF as a rare fibrous growth occurring chiefly in the interscapular and paraspinal regions.1 Our series confirms many of the originally described characteristics of NTF and considerably expands on the clinical and histomorphologic characteristics of this tumorlike process.
NTFs are poorly circumscribed, paucicellular lesions that typically present in the posterior neck and upper back regions. Compared with normal tissue from the nuchal area, NTFs show similar thick collagen fibers. However, in NTF there is an expansion of the collagenized dermis, often with focal lobular architecture, encasement of adnexa, effacement of the subcutis with entrapped adipocytes, and, in some cases, extension into the underlying skeletal muscle. Thus, NTFs appear to represent a localized accentuation of the dense paucicellular, collagenous connective tissue that normally resides in these sites. Compared with true fibrous neoplasms, NTF is much less cellular, suggesting that it represents a peculiar tumorlike reactive process. The tendency of some NTFs to recur probably reflects the persistence of local or systemic factors that initially triggered their development.
In many cases, NTFs contained a localized proliferation of nerve twigs, similar to that seen in traumatic (amputation-type) neuromas; and in some cases, there was also perineurial fibrosis, as seen in Morton's neuroma. These changes may be the result of repetitive minor trauma or a response by small nerves to the local accumulation of collagen.
Of the 52 cases of NTF that we report, 16 examples occurred in extranuchal soft tissue sites. Most of the extranuchal tumors were located in the upper back region, but facial, extremity, and other locations were also encountered. Because the extranuchal lesions were histologically indistinguishable from the nuchal examples, we propose the designation “nuchal-type fibroma (NTF)” to encompass all histologically similar lesions irrespective of their site of origin.
Eleven of 25 patients (44%) in our series with clinical data, and 1 previously reported patient with NTF,2 had diabetes. The high incidence of diabetes in this cohort strongly suggests a nonrandom association.
A link between diabetes and tumorlike changes in fibrous tissues has been established in the case of scleredema.5–7 One patient subcategory affected by this disorder is that of obese adults with maturity-onset diabetes mellitus. The predisposed sites are the skin and underlying soft tissues of the posterior neck, upper back, and shoulders,6, 7 but the process may also involve the face, arms, chest, buttocks, and thighs, as well as other locations.7 Histologically, diabetic scleredema is described as a poorly cellular hyperplasia of the connective tissues, which goes beyond the limits of the dermis and results in replacement of the subcutaneous tissues by coarse collagen fibers. This collagen excess results in marked thickening of the skin.7 One notable histologic feature is the entrapment of skin adnexa and adipose tissue within the dense connective tissue. These findings suggest that diabetic scleredema and NTF have some overlapping features. However, diabetic scleredema is commonly a diffuse or multifocal, indurative process that encompasses a large anatomic region, whereas NTF typically manifests as a localized mass lesion.
Other fibrous lesions associated with diabetes include diabetic mastopathy and the so-called pedunculated lipofibroma. The former often contains a perivascular lymphoid infiltrate and scattered, peculiar, epithelioid fibroblasts.8–11 The latter is a benign, tumorlike hyperplasia of fatty and fibrous tissue analogous to a large, fibroepithelial polyp.12
The increased deposition of collagen that is seen in diabetes-associated fibrous lesions, such as scleredema and NTF, could result from increased collagen synthesis, decreased collagen resorption, or a combination of the two. Increased collagen deposition appears to be mediated by a number of factors, among them transforming growth factor-β (TGF-β), a cytokine that is often present at elevated levels in diabetics. TGF-β is believed to play a role in the fibrogenic complications that occur in these patients. It also has been implicated in other forms of tissue fibrosis that are not associated with diabetes.13, 14
Accumulation of collagen could also result from impairment of the normal enzymatic degradation process due to increased cross-linking of collagen fibers by diabetic, nonenzymatic glycosylation. Collagen resorption may also be impeded by mechanic factors, such as extracellular matrix expansion due to the persistent leakage of anionic proteins from plasma as a result of increased vascular permeability and the trapping of nonglycosylated proteins by glycosylated collagen.15, 16 Finally, tissue ischemia due to microvascular disease could further contribute to a reduction in the normal rate of collagen degradation.
A previously unpublished feature of NTF is its occasional occurrence in the setting of Gardner's syndrome. This disease shows a mendelian dominant pattern of inheritance and is characterized by the association of colorectal adenomatosis with desmoid fibromatosis, keratinous cysts, supernumerary teeth, fibrous dysplasia of the skull, osteomas, and thyroid carcinoma.17–25 In our series, one patient with NTF had definitive evidence of Gardner's syndrome, and two other patients had one or more features of this disease process. The association of NTF with Gardner's syndrome might have been underestimated in our series, because most cases were received in consultation with limited clinical information.
NTF should be distinguished from other fibrous tumors and tumorlike conditions, especially the desmoid-type fibromatosis, circumscribed storiform collagenoma, connective tissue nevus, collagenous fibroma (desmoplastic fibroblastoma), elastofibroma, and fibroma of tendon sheath (Table 2). Although two of our patients who were clinically suspected of having Gardner's syndrome had both NTF and desmoid-type fibromatosis, the lesions were separate, and there were no transitional features suggesting the former to be a degenerative or paucicellular variant of the latter. In our experience, desmoid-type fibromatoses are readily segregated from NTFs, given their predilection for deep soft tissue, substantially greater cellularity, and more prominent, mildly ectatic vessels.
|Nuchal-type fibroma||Collagenous fibroma||Fibroma of tendon sheath||Scar||Elastofibroma||Desmoid-type fibromatosis|
|Most common location(s)||Nuchal region||Shoulder girdle, extremities||Distal extremities, especially the hand||Variable||Subscapular chest wall||Abdominal wall, shoulder girdle|
|Circumscription||No||Yes, by macroscopic appearance, but microscopically infiltrative||Yes||Variable||No||Yes, by macroscopic appearance, but microscopically infiltrative|
|Cellularity||Very low||Increased but generally low||Low to high||Low to high||Low to moderate||Moderate|
|Vascularity and nature of vessels||Very low||Low||Moderate to high, with some slitlike vessels||Variable||Low||Moderate, mildly dilated|
|Appearance of collagen||Bundles of fibers||Amorphous||Amorphous||Amorphous||Amorphous||Amorphous|
|Elastic fibers||Scant||Scant or absent||Absent||Scant to absent||Abundant and abnormal||Absent|
Circumscribed storiform collagenoma (cutaneous sclerotic fibroma) occurs both as a solitary tumor and as a multifocal component of multiple hamartoma syndrome (Cowden's disease).26–31 These lesions differ from NTFs by their dermal-based location, sharp circumscription, whorled or storiform collagen pattern with prominent mucin-filled clefts, and absence of entrapped adipose tissue. They also lack the neural proliferation commonly seen in NTF.
Connective tissue nevi are generally regarded as hamartomatous accumulations of collagen with variable (decreased, normal, or increased) amounts of elastic tissue. These lesions usually present as slightly elevated, small dermal nodules that may cluster to form one or more plaques.32–34 Whereas some authors propose segregation of these lesions based on the relative amount of each connective tissue component, others see no clear advantage to this approach. Connective tissue nevi may be hereditary, as seen with Buschke–Ollendorf syndrome (connective tissue nevi with osteopoikilosis), familial cutaneous collagenoma (multiple connective tissue nevi of the collagen type symmetrically distributed on the trunk and upper arms), and tuberous sclerosis (collagen nevus/shagreen patch in association with other abnormalities, including gliomas, rhabdomyomas, angiomyolipomas, and cutaneous angiofibromas). These lesions differ histologically from NTFs in that they are generally smaller, more superficial, and less permeative and lack deep subcutaneous extension.
Collagenous fibroma (desmoplastic fibroblastoma) is a benign soft tissue tumor with a wide anatomic distribution, predominance in males, and peak incidence in the fifth and sixth decades of life.35 This process predominantly affects the subcutis, although fascial involvement is common and muscle is affected in approximately 20% of cases. Collagenous fibromas differ from NTFs in several respects. First, at low magnification, the lesions often appear well marginated, though on closer inspection entrapment of adipocytes and other structures is common. Second, the tumors contain moderate numbers of bland, stellate, and spindled fibroblasts embedded in a more homogeneous collagenous or myxocollagenous matrix.35–37
Elastofibroma generally presents as an ill-defined mass involving the infrascapular chest wall of middle-aged and elderly adults.38, 39 Microscopically, this process consists of an admixture of intertwining collagen fibers, fragmented elastic fibers, and scattered fibroblasts. The elastic fibers are best seen with an elastic stain (e.g., Verhoeff's or Gomori's stains) and have a characteristic appearance with a central core and peripherally radiating (spokelike) filaments; a structural resemblance to chenille fibers or pipe cleaners has been noted. NTFs are less cellular than elastofibromas and contain only a delicate network of thin, elastic fibers of normal width, aligned parallel to the collagen fibers.
Fibroma of tendon sheath occurs mainly in the distal extremities and presents as a discrete, often lobulated nodule that is generally attached to the surface of a tendon.40, 41 Among the more than 1000 “fibromas” on file in the Soft Tissue Registry of the Armed Forces Institute of Pathology, this is the most common subtype, accounting for approximately 40% of all cases. It differs clinically from the nuchal-type fibroma in its anatomic distribution, tendency to involve deeper soft tissues, and predilection for younger patients, with a peak incidence in the third decade of life. Histologically, it is better marginated, often with peripheral cleftlike vascular spaces, and much more cellular, with early stages often resembling nodular fasciitis or fibrous histiocytoma. In addition, it has more homogeneous, amorphous collagen than nuchal-type fibroma.
Because NTFs often contain some entrapped subcutaneous fat, one might also consider a fibrolipoma in the differential diagnosis. The latter tumor type can be seen in the upper back and nuchal region, but it differs from NTF in several ways. First, subcutaneous fatty tumors are usually better marginated and generally do not exhibit substantial dermal involvement. Second, they typically contain more abundant adipose tissue. Finally, the collagenous element often contains more abundant fibroblasts.
In conclusion, our series of 50 patients with 52 NTFs indicated the following: These lesions have a predilection for the posterior neck, but they may also involve other soft tissue sites, such as the upper back, shoulder, and facial regions. The designation we have adopted is in keeping with this observation. The process typically presents as a mass lesion and represents a nonneoplastic, tumorlike accumulation of collagen. A frequent association with diabetes and a weaker link to Gardner's syndrome are documented.