Primary Cutaneous Ewing Sarcoma of the Scalp With Metastasis to the Lung: An Unusual Manifestation During Pregnancy.

ABSTRACT: A 32-year-old G2P1L1 (5 months pregnant) woman presented with a 3-month history of a slow-growing cystic lesion on her scalp vertex. Similar lesions in the exact location were excised twice in the past with a diagnosis of trichilemmal carcinoma (TC). A biopsy of the scalp lesion showed morphology and immunoprofile consistent with previously diagnosed TC. Staging PET/CT demonstrated a 4.7 cm right upper lobe lung, and a subsequent lung biopsy showed a small, round blue-cell tumor with necrosis, morphologically identical to the prior biopsies from the scalp. Considering the unusual clinical course of TC, a lung biopsy was sent for next-generation sequencing that showed EWSR1-FLI1 (type1) fusion. Additionally, CD99 immunostaining revealed uniform cytoplasmic and membranous staining in the tumor cells. The previous scalp excision specimen was also sent for mutation analysis, which showed EWSR1-FLI1 fusion. In conjunction with clinical history and histological and molecular findings, a definitive diagnosis of primary cutaneous Ewing sarcoma (PCES) with local recurrence and metastasis to the lung was made. We present a case of PCES, which was previously misdiagnosed and treated as TC. This case emphasizes the importance of CD99 in the initial screening of cutaneous small round blue-cell tumors to avoid misdiagnosis from other morphological overlaps. Also, despite its rarity, PCES should be included in the differential diagnosis of small, round, blue cell tumors at cutaneous sites. Our case also exemplifies common biases in medical decision-making, including premature closure and anchoring bias which can result in misdiagnosis or diagnostic delay and associated delay in appropriate management.

Circulating histocompatibility antigen (HLA) gene products may help differentiate benign from malignant indeterminate pulmonary lesions.

BACKGROUND: This study explores the potential diagnostic utility of soluble Human Leukocyte Antigen (sHLA) molecules differentially released by lung adenocarcinoma and benign lung lesions. METHODS: Conditioned media from the NSCLC cell lines H358 and H1703 were immunoblotted for soluble isoforms of major histocompatibility complex (MHC) class I (ABC) and II (DRB1, DMB, and DQ) antigens. Sera from 25 patients with benign and 25 patients with malignant lesions were similarly evaluated to appraise the potential diagnostic value. RESULTS: Higher concentrations of soluble HLA class I molecules were observed in conditioned medium for the highly-invasive H1703 cell line, relative to the more indolent H358 cells. Evaluation of these markers against a cohort of 50 cases demonstrated that patients with malignant lesions possess higher levels of HLA class I and II molecules relative to those with benign lesions (p < 0.05), with exception to the primary isoform, DQA1, which was suppressed in malignancies. An analysis of biomarker performance via ROC analysis revealed promising performance (AUC > 0.75) for DMB and the 26 kDa isoform of DQ in distinguishing lesion pathology. CONCLUSIONS: Soluble HLA molecules may have diagnostic value for early-stage NSCLC. Validation studies are currently underway using sera from a lung cancer screening cohort.