Atypical Fibroxanthoma Invading Parietal Bone

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.

The Utility of Bone Burring for the Clearance of Locally Advanced Scalp Malignancies: A Scoping Review

The scalp harbors a range of neoplasms occurring at inordinate rates and associated with poorer outcomes. Its unique anatomy poses surgical challenges, including clear deep margins when resecting these lesions. For malignancies extending to the pericranium, removal of outer cortical cranial bone is ideal and routinely achieved with a burr. This review aims to investigate the literature to ascertain the utility and safety of this technique while highlighting evidence gaps.

Methods

A literature search was conducted systematically using MEDLINE, Embase, and PubMed. Articles were reviewed for inclusion, and eligible studies were analyzed for study design, patient and intervention details, and outcome measures. A formal statistical analysis was not conducted.

Results

The original search yielded 1506 unique results, and eight studies met the inclusion criteria: four case series, two retrospective analysis of records, two case reports. A number of tumor types were identified, but the burring method used was consistent in all studies. Despite reassuring primary outcome measure results, specifically in terms of local control rates, the overall evidence quality is limited by the nature of the included studies. Few adverse events were reported.

Conclusions

Evidence for the oncological efficacy of scalp bone burring remains limited. Although the technique seems relatively safe, further investigation is required into its utility and drawbacks. Future studies should aim to report more technical details and more information about outcomes. It may also be worth comparing burring to alternatives such as outer cortical splitting, curettage, and high-dose curative radiotherapy.

[Atypical fibroxanthoma]

Atypical fibroxanthoma (AFX) is a rare skin tumor characterized by a combination of a «malignant» morphological features and non-aggressive clinical course. Diagnosing AFX is challenging due to histological «diversity» and heterogeneous immunophenotype. The presented review describes the history and evolution of AFX as a nosological form of cancer, its histogenetic origin, pathogenesis and biological potential. The clinical, morphological, immunohistochemical, molecular cytogenetic characteristics and histological subtypes of the tumor as well as differential diagnosis have been presented in detail.

Surgical Management of Invasive Atypical Fibroxanthomas/Undifferentiated Pleomorphic Sarcomas of the Scalp: A Systematic Review Comparing Outer Table Resection to Full-Thickness Craniectomy

Invasive atypical fibroxanthomas and undifferentiated pleomorphic sarcomas of the scalp are relatively rare spindle cell tumors that recur at high rates. Wide local excision and Mohs surgery alone are not feasible for the definitive management of lesions adhering to the underlying pericranium and/or calvarium. This brief clinical study presents 2 patient cases and includes a systematic review of the literature. In our literature review, 2 of 4 patients treated with outer table resection had no disease recurrence, 1 died due to an unrelated cause, and 1 died due to disease progression. Three of 9 patients treated with full-thickness craniectomy had no disease recurrence, 5 patient outcomes were not specified, and 1 died from disease progression. There are currently no recommendations for the management of these invasive scalp lesions. We believe invasive atypical fibroxanthomas/undifferentiated pleomorphic sarcomas of the scalp without frank calvarial involvement can be effectively treated with outer table resection.

Surgical excision margins for fibrohistiocytic tumors, including atypical fibroxanthoma and undifferentiated pleomorphic sarcoma: A probability model based on a systematic review

BACKGROUND

Mohs micrographic surgery or wide local excision is the treatment of choice for fibrohistiocytic tumors with metastatic potential, including atypical fibroxanthoma (AFX) and cutaneous undifferentiated pleomorphic sarcoma (cUPS). Since margin clearance is the strongest predictor of clinical recurrence, improved recommendations for appropriate surgical margins help delineate uniform excision margins when intraoperative margin assessment is not available.

OBJECTIVE

To determine appropriate surgical wide local excision margins for AFX and cUPS.

METHODS

Literature search (Ovid MEDLINE, Embase, Web of Science, and Cochrane Library from inception to March 2020) to detect case-level data. Estimation of margins required using a mathematical model based on extracted cases without recurrences.

RESULTS

Probabilistic modeling based on 100 cases extracted from 37 studies showed peripheral clearance margin (ie, wide local excision margin) calculated to clear 95% of all tumors was 2 cm for AFX and 3 cm for cUPS. AFX tumors 1 cm or less required a margin of 1 cm.

LIMITATIONS

Data were extracted from published cases.

CONCLUSIONS

Atypical fibroxanthoma removed with at least a 2-cm peripheral excision margin is less likely to recur. Smaller tumors 1 cm or less can be treated with a more conservative margin. Margin-control surgical techniques are recommended to ensure complete removal while minimizing surgical morbidity.

Right Parietal Skull Xanthoma Characterized as a Metastatic Deposit

BACKGROUND

Xanthomas are benign lipomatous deposits that can be found systemically in various tissues including bones. Their presence in the skull remains a rare entity. Despite their benign characteristics, imaging modalities are often unable to distinguish them from malignant lesions. This leads to a diagnostic dilemma in patients with underlying malignancy. This case report highlights such a case where clinical history of prostate cancer and image findings were concordant with that of metastatic deposit in the parietal skull region.

CASE DESCRIPTION

This 65-year-old gentleman was diagnosed with prostatic adenocarcinoma. During systemic workup for his tumor, he was found to have a right parietal skull lesion. Magnetic resonance imaging of the brain, as well as a bone scan, were consistent with that of a metastatic deposit. As treatment would be drastically affected by the diagnosis, an excision biopsy was performed. The histology was consistent with that of a bone xanthoma.

CONCLUSIONS

Xanthomas are benign lesions that can be seen deposited in appendicular and axial skeleton. Skull lesions are rare with most case descriptions focusing on their presence in the frontoorbital regions and mandible and temporal bone. They usually have a benign course but may present with symptoms due to localized mass effect. Surgical intervention and histologic diagnosis may still be required in these lesions due to their lack of imaging characteristics that confirm their diagnosis through noninvasive methods.