Giant Ulcerated Polypoidal Cellular Fibrous Histiocytoma and Clustered Multiple Cellular Fibrous Histiocytomas in Segmental Distribution: An Uncommon Presentation with Benign Biological Behaviour

Sir, Cellular fibrous histiocytoma (dermatofibroma) was first described by Calonje et al.,[1] a distinct variant of fibrous histiocytoma. It is usually less than 3 cm in size. A giant fibrous histiocytoma is a rare clinical variant of fibrous histiocytoma, which is characterized by an unusually large size (>5 cm), pedunculated appearance and benign biological behaviour despite its size. A 40-year-old man came to the dermatology department with the complaint of a fleshy mass over the right hip for 10 years. The patient was apparently alright 10 years back; then, he noticed a pea-sized nodule over the right hip, which gradually grew to attain its present size, associated with itching and bloody discharge. Examination revealed multiple nodules over the right hip. The largest nodule was oblong, fleshy, ulcerated and pedunculated mass measuring 8 cm × 5 cms in size, firm in consistency and non-tender. There were multiple clustered hyperpigmented nodules adjacent to the pedunculated nodule varying from 1 to 5 cm in size with smooth surface and firm consistency [Figure 1a]. Dimpling skin on lateral pressure or Fitzpatrick’s sign could not be elicited as the tumour was large and ulcerated. Regional lymph nodes were not enlarged. He was provisionally diagnosed with dermatofibrosarcoma protuberans (DFSP). Routine haematological, biochemical investigations, X-ray chest and ultrasonography of the abdomen revealed a normal study. Lesional biopsy revealed diffuse infiltration of spindle-shaped cells in the dermis and subcutis. Some of the spindle-shaped cells showed the formation of fascicles with low mitotic activity. Stroma was collagenous with blood vessels [Figure 1b and c]. Immunohistochemistry study showed cluster of differentiation 10 (CD10) positivity [Figure 2a], cluster of differentiation 34 (CD34) showed peripheral positivity [Figure 2b], smooth muscle actin (SMA) showed focal area positivity [Figure 2c], and signal transducer and activator of transcription 6 (STAT6) was weak positive [Figure 2d]. S100 [Figure 3a] and Desmin were negative [Figure 3b]. Proliferative activity of the tumour, Ki-67, was <2% [Figure 3c]. Immunohistochemistry with factor XIIIa could not be conducted due to non-availability. Histopathology and the immunohistochemical study confirmed the diagnosis of deep cellular fibrous histiocytoma. He was referred to the department of surgery, where the tumour was completely excised along with a 3 cm margin [Figure 3d].Figure 1: (Original) (a) Large ulcerated polypoidal fleshy nodule and multiple hyperpigmented nodules over the right hip. (b) Histopathology of fleshy nodule. Dermis and subcutis show diffuse infiltration of spindle-shaped cells. Some of the spindle-shaped cells showed the formation of fascicles. (H and E stain, x10) (c) Histopathology of fleshy nodule. Diffuse infiltration of spindle-shaped cells; some of them show fascicle formation and exhibiting low mitotic activity. Collagenous stroma with blood vessels is seen. (H and E stain ×40)Figure 2: (Original) (a) Immunohistochemistry showing CD10 positivity. (x40) (b) Immunohistochemistry showing CD34 peripheral positivity. (x40) (c) Immunohistochemistry showing SMA positivity in focal area. (x40) (d) Immunohistochemistry showing STAT6 weak positivity. (x40)Figure 3: (Original) (a) Immunohistochemistry showing S100-negative. (x40) (b) Immunohistochemistry showing Desmin-negative. (x40) (c) Immunohistochemistry showing Ki, proliferating activity of tumour. (x40) (d) Tumour after surgical excisionA giant cellular fibrous histiocytoma is a benign tumour most often found in middle-aged adults and has a slight female preponderance. The majority of the lesions are asymptomatic and located on the extremity or trunk. The pathogenesis of fibrous histiocytoma is unsettled. Some researchers consider it a neoplastic, while others consider it a reactive process.[2] The proponents of the neoplastic theory base their argument on its inability to regress spontaneously.[3] The exponents of reactive process theory consider local trauma, such as insect bite or vaccination in the pathogenesis of fibrous histiocytoma.[3] Histopathological variants of fibrous histiocytoma described include common, aneurysmal, hemosiderotic, epithelioid, cellular, lipidized, atrophic, clear cell, palisading, myxoid, ballooning, signet ring cell and keloidal variant. Incidentally, Han et al.[4] reported cellular fibrous histiocytoma in 11.5% of cases in their clinico-histopathological study of 122 cases of benign fibrous histiocytoma. Ulceration in fibrous histiocytoma is rare; however, ulceration was noted in the index case. Interestingly, clustering of fibrous histiocytomas in segmental distribution was observed in the index case. The cellular variant of fibrous histiocytoma is characterized by high recurrence (26%) in contrast to low recurrence (1%) in fibrous histiocytoma. Histologically, the lesions of cellular fibrous histiocytoma are highly cellular, with a more prominent fascicular growth pattern. The tumour cells tend to have more eosinophilic cytoplasm and infiltrate into the subcutis. The main differential diagnosis includes DFSP and leiomyosarcoma. DFSP shows extensive replacement of subcutis and diffuse CD34 positivity and monomorphous storiform growth pattern with monomorphic cells and cytogenic evidence of t (17;22) translocation. Leiomyosarcoma shows spindle cells with cigar-shaped nuclei, cytologic atypia, more uniform fascicular growth, and more diffuse SMA and Desmin-positive cells. Rarely, fibrous histiocytoma may metastasize to lymph nodes, lungs, brain and liver.[5] Notably, there is no evidence of metastasis in lymph nodes or lungs in the index case. Interestingly, Dunkin et al.[6] have reported metastasis in the lungs, anterior abdominal wall and posterior chest wall 30 months after excision of the primary tumour. Complete excision with a 3 cm margin surrounding the tumour, including subcutaneous fat, is the ideal procedure for fibrous histiocytoma. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.