Lung adenocarcinoma metastasizing to fibrous histiocytoma: A case report

RATIONALE: Tumor-to-tumor metastasis is an uncommon phenomenon, and the tumor metastatic to mesenchymal tumor is extremely rare. To our knowledge, this is the first case of lung adenocarcinoma metastasizing to fibrous histiocytoma. PATIENT CONCERNS: A 58-year-old Chinese woman was admitted to our hospital with a complaint of progressive enlargement of a mass in the right upper arm without pain, heat (localized warmth), redness, and swelling, for a year. DIAGNOSES: Ultrasound revealed a mass with relative clear boundary in the right upper arm near elbow joint. Uneven echoes, and blood flow signals were showed within the mass. The tumor was well-demarcated from the surrounding tissue a thin fibrous capsule. Scattered enlarged cells with hyperchromatic pleomorphic nuclei were dispersed in an otherwise typical cutaneous fibrous histiocytoma. These atypical cells arranged in poorly glandular structures or irregular epithelioid nest and were demonstrated as metastatic lung adenocarcinoma by immunohistochemical staining. We reviewed the biopsy section and found these 2 sites of adenocarcinoma shared similar histologic morphological features. Therefore, the final diagnosis was lung adenocarcinoma metastasizing to fibrous histiocytoma. INTERVENTIONS: The patient was diagnosed with lung adenocarcinoma by bronchoscopic biopsy 3 months ago and received 4 cycles of NP (Vinoreltraye [NVB] + cis-platinum) chemotherapy program. The patient underwent a total resection of the mass in right upper arm. OUTCOMES: The patient died of multiple organ failure after 10 months since she was diagnosed as lung adenocarcinoma. LESSONS: The accumulation of lipid droplets in fibrous histiocytoma may be a potential reason for modifying pre-metastatic niche, and therefore create a tumor microenvironment suitable for metastasis.