Superficial CD34-Positive Fibroblastic Tumor: A Case Report and Review of the Literature. Am J Dermatopathol. 2020;42:68-71. [PMID: 30702454 DOI: 10.1097/dad.0000000000001355]

Clinicopathologic and molecular study of superficial CD34-positive fibroblastic tumours mimicking atypical fibrous histiocytoma (dermatofibroma)

AIMS

Superficial CD34-positive fibroblastic tumour (SCD34FT) is an uncommon but distinctive low-grade neoplasm of the skin and subcutis that shows frequent CADM3 expression by immunohistochemistry (IHC). In this study, prompted by an index case resembling 'atypical fibrous histiocytoma (FH)' that was positive for CADM3 IHC, we systematically examined a cohort of tumours previously diagnosed as 'atypical FH' by applying CADM3 and fluorescence in situ hybridization (FISH) for PRDM10 rearrangement, to investigate the overlap between these tumour types.

METHODS AND RESULTS

Forty cases of atypical FH were retrieved, including CD34-positive tumours (n = 20) and CD34-negative tumours (n = 20). All tumours were stained for CADM3. All CADM3-positive tumours were evaluated by FISH to assess for PRDM10 rearrangement. Eleven CD34-positive tumours (11/20, 55%) coexpressed CADM3 and were reclassified as SCD34FT. None (0/20) of the CD34-negative atypical FH were CADM3-positive. Reclassified SCD34FT (10/11) arose on the lower extremity, with frequent involvement of the thigh (n = 8). Features suggestive of atypical FH were observed in many reclassified cases including variable cellularity, spindled morphology, infiltrative tumour margins, collagen entrapment, epidermal hyperpigmentation, and acanthosis. Variably prominent multinucleate giant cells, including Touton-like forms, were also present. An informative FISH result was obtained in 10/11 reclassified tumours, with 60% (6/10) demonstrating PRDM10 rearrangement.

CONCLUSION

A significant subset of tumours that histologically resemble atypical FH, and are positive for CD34, coexpress CADM3 and harbour PRDM10 rearrangement, supporting their reclassification as SCD34FT. Awareness of this morphologic overlap and the application of CADM3 IHC can aid the distinction between SCD34FT and atypical FH.

Superficial CD34-Positive Fibroblastic Tumor: A Newly Recognized Entity With Overlapping Features of PRDM10-Rearranged Soft Tissue Tumors

Superficial CD34-positive fibroblastic tumor (SCPFT) is a recently identified, infrequent, low-grade mesenchymal neoplasm, first identified in 2014. Although it is relatively new to the field, SCPFT has been gaining prominence in surgical pathology practice because of its distinctive features. As of now, there are limited reported cases of SCPFT, with fewer than 100 instances documented in scientific literature. This distinctive blend of rarity and intriguing variability in presentation emphasizes the significance of identifying and understanding this uncommon entity, facilitating precise diagnosis and optimal management. In this article, we aimed to present a notable case of SCPFT in a male in his 20s who presented with a distinct subcutaneous mass measuring 2.4 × 1.8 cm at the medial aspect of the knee joint. The patient reported no significant medical history or trauma to the affected area. MRI of the knee showed a well-defined 2.4 × 1.8 cm subcutaneous mass with no definite communication with the underlying ligament or meniscus. The histopathological examination revealed spindle cell neoplasm arranged in intersecting fascicles, accompanied by arborizing blood vessels. Neoplastic spindle cells exhibited marked nuclear pleomorphism, and abundant and eosinophilic cytoplasm, with focal areas of granular, glassy, and lipidized cytoplasm. Nuclear pseudo inclusions and a few mitotic figures (1-2 per high-power field) were noted. Inflammatory infiltrates were identified within the neoplasm, comprising eosinophils and lymphocytes, highlighting an immune response within the tumor microenvironment. The surgical margin exhibited involvement with the tumor infiltrates, with the neoplastic cells extending into the adjacent fat tissue. This finding indicates local tumor spread and potential challenges in achieving complete resection. Immunohistochemical staining showed positive staining for CD34, corroborating the diagnosis of a CD34-positive fibroblastic tumor. Focal positive staining for pan-CK was noted. Staining for CD31, smooth muscle actin (SMA), desmin, S100, and anaplastic lymphoma kinase (ALK) was negative, supporting the diagnosis. The Ki67 proliferation index was low.

An update on selected cutaneous (myo) fibroblastic mesenchymal tumors

Cutaneous (myo)fibroblastic tumors constitute a group of tumors with overlapping clinicopathological features and variable biologic behavior. In the present review we focus on the histomorphology, immunohistochemical profile and molecular background of the following entities: dermatofibrosarcoma protuberans (DFSP), CD34-positive fibroblastic tumor (SCD34FT), myxoinflammatory sarcoma (MIFS), low-grade myofibroblastic sarcoma, solitary fibrous tumor and nodular fasciitis. Although some of these entities typically arise in deep-seated locations, they may occasionally present as cutaneous/superficial tumors and might be challenging to recognize. This review covers in depth the latest advances in molecular diagnostics and immunohistochemical markers that have significantly facilitated the correct classification and diagnosis of these neoplasms.

Superficial CD34-Positive Fibroblastic Tumor: Two Case Reports

Superficial CD34-positive fibroblastic tumor (SCPFT) is a recently described disease entity characterized by marked nuclear pleomorphism, low mitotic count, and diffuse CD34 positivity. It is a rare, distinctive, low-grade fibroblastic neoplasm. To date, only 44 cases have been reported in the English-language literature. Herein, we report two cases of SCPFT involving a 48-year-old male and a 22-year-old male with superficial tumors on the right and left thighs, respectively. Excision was performed in both cases. Histologically, both tumors showed spindle-to-epithelioid cells arranged in fascicular or sheet-like patterns. Most cells displayed granular or eosinophilic glassy cytoplasm, marked nuclear pleomorphism, and a low mitotic rate. On immunohistochemical staining, tumor cells were diffusely positive for CD34 and negative for S100 protein, smooth muscle actin, and desmin. After wide excision, neither patient experienced recurrence or metastasis after 16 months and 11 months of clinical follow-up, respectively. To the best of our knowledge, these are the first two cases of SCPFT reported in Korea. We believe these case reports would contribute to the clinicopathological understanding of SCPFT and assist clinicians in differentiating this tumor from other superficial soft tissue neoplasms.

Superficial CD34-positive fibroblastic tumor (SCPFT): A review of pathological and clinical features

Superficial CD34-positive fibroblastic tumor (SCPFT) is a recently described rare mesenchymal tumor of borderline malignancy. It generally involves superficial soft tissue, with a predilection to the lower extremities. Microscopically this tumor is characterized by a fascicular and storiform growth pattern, spindled to epithelioid cells, nuclear atypia with pleomorphism, and eosinophilic granular, and fibrillar to glassy cytoplasm. Strong diffuse immunoreactivity for CD34 is very characteristic of this entity. Due to under-recognition, this tumor is generally underreported. Additionally, cases of recurrence are rarely reported in the literature. We will comprehensively review the English language literature on all reported cases of SCPFT, with emphasis on recurrence.

Superficial CD34-Positive Fibroblastic Tumor on the Chest Wall of an 8-Year-Old Girl: A Case Report and Literature Review

This study reports a case of superficial CD34-positive fibroblastic tumor (SCPFT) in a child and analyze the major known clinicopathological features of SCPFT and other skin mesenchymal tumors, contributing to an accurate diagnosis of this rare disease. We summarize the clinicopathologic features of an 8-year-old girl who was diagnosed with SCPFT and 46 previously reported SCPFT cases. Post-operative histopathologic examination of the current case showed the tumor lesion was well-circumscribed; tumor cells were spindled-to-polygonal with a fascicular pattern; most nuclei displayed hyperchromasia and low mitotic rate; intranuclear pseudoinclusions could be found; and abundant eosinophilic cytoplasm and partial myxoid stroma were observed. Immunohistochemistry revealed strong and diffuse CD34-positivity, vimentin staining positively but no S-100, SMA, NSE, CD31, desmin, cytokeratin, STAT6, β-catenin, MDM2, or ERG expression. The Ki-67 and CD68 labeling indexes were approximately 1%. There were no rearrangements of PDGFB or PRDM10 tested by FISH. After surgical resection, the patient had no signs of recurrence or metastasis at a 6-month follow-up. The present case is the first that describes SCPFT in children and has significant clinical implications. SCPFT should be differentiated from other skin mesenchymal tumors. The presented compilation of all so far published SCPFT cases will help in diagnosing successfully SCPFT and increasing awareness of this tumor to guide clinical practice.

Perianal superficial CD34-positive fibroblastic tumor: A case report

BACKGROUND

Superficial CD34-positive fibroblast tumors (SCPFTs) are newly recognized fibroblast and myofibroblast tumors representing intermediate tumors. To the best of our knowledge, fewer than 50 cases have been reported. Perianal SCPFT has not been previously reported.

CASE SUMMARY

A 55-year-old man was hospitalized upon discovering a painless perianal lump 10 d prior. Physical examination showed a lump of approximately 3 cm × 4 cm in the 7 to 8 o’clock direction in the perianal area. Perianal abscess was considered the primary diagnosis. Lump removal surgery was performed under epidural anesthesia. Postoperative pathology showed a well-circumscribed, soft tissue-derived, spindle-cell tumor with strong CD34 positivity by immunohistochemistry. The final diagnosis was perianal SCPFT. There were no complications, and the patient was followed for more than 8 mo without recurrence or metastasis.

CONCLUSION

We report a case of perianal superficial CD34-positive fibroblast tumor. This rare mesenchymal neoplasm has distinctive histomorphology, which is important for diagnosis. Comprehensive consideration of clinical information, imaging, histology, and immunohistochemistry is important for diagnosis.