Clear cell atypical fibroxanthoma: a case report and review of the literature

A Tale of Two Tumors: A Collision Tumor of Atypical Fibroxanthoma and Basal Cell Carcinoma

ABSTRACT

A collision tumor is an infrequent phenomenon characterized by the presence of 2 histologically distinct tumor types (either benign or malignant) occurring within the same specific anatomical site. We describe a rare case of co-occurrence of basal cell carcinoma and atypical fibroxanthoma presenting as a single lesion on the scalp in a 76-year-old man. The lesion was clinically suspicious for basal cell carcinoma and biopsied. Histologic examination showed 2 distinct tumors, one with basaloid cells and the other one with pleomorphic spindle cells colliding and growing together. Immunohistochemical stains were crucial in establishing the diagnosis. This presentation is exceedingly rare and requires additional evaluation for diagnosis.

Keloidal atypical fibroxanthoma of the scalp

Atypical fibroxanthoma (AFX) is a rare low-grade sarcoma that occurs mainly in the elderly and may recur locally. There are multiple variants including keloidal AFX (KAF). KAF is characterised by a proliferation of atypical spindled and epithelioid cells admixed with bizarre pleomorphic cells. These cells intersect among broad bands of keloidal collagen. AFX is a diagnosis of exclusion so a broad panel of immunohistochemical staining should be applied to rule out other differentials (squamous cell carcinoma (SCC), melanoma, leiomyosarcoma, etc). There is added difficulty with the diagnosis of KAF as it may mimic multiple keloidal lesions, including exuberant scarring, as in this case. p53 immunohistochemistry staining can be useful in highlighting the presence of tumour cells. Additionally, next generation sequencing can detect genetic mutations identified in clonal proliferations consistent with tumour formation. KAF is easily overlooked and it should be included in the differential diagnosis for keloidal lesions showing even mild atypia.

Collision Tumor Comprised of Atypical Fibroxanthoma and Invasive Squamous Cell Carcinoma: A Case Report of an Extremely Rare Entity

Single benign or neoplastic dermal lesions are very common. Lesions with two distinct tumors occurring as a single entity are extraordinary and known as collision tumors. In the present case, the lesion was diagnosed on biopsy, and later, wide local skin excision was performed. Excision revealed that the lesion was composed of two distinct cell populations exhibiting the characteristics of two separate neoplastic entities. The histopathology revealed a single lesion comprised of moderately differentiated squamous cell carcinoma that appeared to invade an atypical fibroxanthoma. This is unprecedented in the English literature and the first such case to be reported.

Case for diagnosis. Atypical fibroxanthoma

Atypical fibroxanthoma is a rare superficial fibrohistiocytic tumor. Clinically, it presents itself as a painless, solitary, ulcerated, and slow-growing nodule found mainly on sun-exposed areas - especially of the head and neck - of elderly individuals. The diagnosis is based on histopathological and immunohistochemical features. Immunohistochemical staining plays a critical role for the exclusion of differential diagnoses. Since atypical fibroxanthoma has an indolent clinical course, surgical excision is adequate for treatment. We present a case of atypical fibroxanthoma on the ear of a patient.

An Unusual Case of Pinna Squamous Cell Carcinoma Arising Shortly after Resection of Atypical Fibroxanthoma

Objective

To report a unique case of pinna squamous cell carcinoma (SCC) arising shortly after resection of atypical fibroxanthoma (AFX) at the same site.

Case report

An 81-year-old gentleman presented with a nodular right pinna lesion. This was excised, and histology confirmed AFX. Ten weeks later, an ulcerative lesion appeared at the resection site. This was confirmed to be SCC. Comparative analysis revealed no morphological resemblance between the initial AFX and new SCC lesion, and there was no evidence of initial misdiagnosis.

Conclusion

SCC is the most common cancer involving the pinna. Whilst prolonged sun exposure is an important risk factor for SCC, chronic inflammation and wounds are other potential sources. We postulate whether SCC could have arisen from the previous scar tissue in a manner similar to Marjolin's ulcer. This would be a highly unusual finding in the pinna and to our knowledge unprecedented in the English literature.

Clear-cell atypical fibroxanthoma: An unusual case in an unusual place

Atypical fibroxanthoma represents a low-grade sarcoma that usually presents in the elderly population on sun-damaged areas of the head and neck regions. This neoplasm is characterized on histology by atypical pleomorphic, epithelioid to spindled cells, arranged in a haphazard pattern, set within a background of solar elastosis. In this case report, we present a unique case of the rare variant of clear-cell atypical fibroxanthoma arising in an unusual place, specifically the lower extremities.

Primary dermal pleomorphic liposarcoma: utility of adipophilin and MDM2/CDK4 immunostainings

Liposarcoma, usually arises in deep soft tissues and pleomorphic liposarcoma (PL), is the rarest histopathologic variant. However, 15 cases of entirely dermal PL have been reported. We describe a case of a 79-year-old man who developed a rapidly growing nodule on his thorax. Excisional biopsy was performed and immunohistochemical studies were carried. The lesion was a well-circumscribed dermal nodule composed of multivacuolated pleomorphic lipoblasts and atypical mitotic figures. Neoplastic cells expressed CD10 and resulted negative S100 protein, Melan-A, MITF-1, AE1/AE3, CD4, CD68 (PGM1), retinoblastoma gene family protein, pericentrine and lysozyme. Adipophilin stain showed the lipid contents in the cytoplasm of the neoplastic cells. MDM2 and CDK4 resulted both negative. A diagnosis of primary dermal PL was made. This case shows the utility of adipophilin immunostaining to prove the lipid contents in neoplastic cells, which has the advantage of using formalin-fixed paraffin-embedded tissue and making needless frozen sections and ultrastructural studies to show these findings. Negative MDM2/CDK4 staining in our case argues against the possibility of dedifferentiated liposarcoma and further supports the diagnosis of true PL.