Case Report: Paraneoplastic psoriasis in thymic carcinoma

Abstract

Thymic carcinomas are exceedingly rare and very aggressive malignancies of the anterior mediastinum. While thymomas exhibit a high association with paraneoplastic syndromes, these phenomena are a rarity in thymic carcinomas. In general, acanthotic syndromes such as acroceratosis neoplastica and acanthosis nigricans maligna are commonly observed as paraneoplastic phenomena in patients with carcinomas. In contrast, psoriasis vulgaris, another acanthotic disease, rarely occurs as a paraneoplasia. We report the case of a 36-year-old patient with progressive thymic carcinoma (undifferentiated carcinoma, T3N2M1a) and paraneoplastic psoriasis occurring ten months before the initial diagnosis of the carcinoma. Over the course of the disease, new psoriatic flares heralded relapse or progression of the carcinoma. To our knowledge, this is the first reported case of paraneoplastic psoriasis in thymic carcinoma.

Keywords: ADOC; mediastinal tumor; paraneoplastic syndrome; psoriasis; thymic carcinoma; thymic epithelial tumors.

Figure 1

Clinical findings at first presentation and histological findings in a punch biopsy of 4mm: Bilateral erythematous, slightly scaling plaques on elbows (A) and knees (B) in a 36-year-old patient with thymic carcinoma, without affection of mucous membranes, nail involvement or arthritis. Psoriasiform acanthosis with perivascular lymphocytic infiltration at the upper corium (C) (HE, bar 250µm). Magnified depiction of psoriasiform acanthosis with parakeratotic horn and prominent capillary vessels in the papillary dermis, furthermore collection of neutrophils in the stratum corneum (arrow) (HE stain, bar 50µm) (D).

Figure 2

Radiological findings upon initial diagnosis of thymic carcinoma (A, B) Baseline hybrid PET/CT: (A) Axial contrast-enhanced CT scan demonstrates the large thymic carcinoma mass with sub-total collapse of main bronchi and superior vena cava syndrome (arrow). Influx of i.v. contrast agent applied in left cubital vein via muscular and thoracical veins (star). (B) Corresponding 18F FDG-PET fusion overlay indicates high metabolic activity of the tumor (yellow).

Figure 3

Histological findings of an undifferentiated thymic carcinoma in a CT-guided biopsy of the mediastinal mass upon initial diagnosis: (A) HE stain; Tumor islands on a fibrotic background. Small to mid-sized tumor cells with scant eosinophilic cytoplasm and small, ovaloid to spindly, chromatin-dense nuclei. Mitoses are rarely seen. No necrosis. (B) Pan-Cytokeratin (AE1/AE3); Diffuse and strong cytoplasmic expression. (C) CD117/c-kit; Diffuse and strong cytoplasmic and membranous expression. (D) GLUT-1; Diffuse and moderate to strong membranous expression. (E) PAX5; Focal, heterogeneous, moderate nuclear expression. (F) CD5; Tumor cells negative (T-cells as positive internal control).

Figure 4

Graphical depiction of treatment of thymic carcinoma, course of psoriasis and course of thymic carcinoma; x-axis= type of systemic therapy, intensity of psoriatic lesions (pink= maximum, white= minimum); y-axis= time in months from September 2019 to March 2023; CT= computed tomography; PET= PET/CT, positron emission tomography and CT; irradiation= three weeks of mediastinal irradiation with 35 Gy; surgery= excision of mediastinal residues, along with parts of pericardium and pleura and adjacent adipose tissue; PAC= cisplatin, doxorubicin, vincristine and cyclophosphamide for six cycles (with a total dosis of 36 mg of dexamethasone per cycle) and irradiation between cycles one and two; Pacli/Carbo= three cycles of carboplatin (AUC6) and paclitaxel (with a cumulative dosis of 32 mg of dexamethasone per cycle), followed by three cycles of carboplatin (AUC6) and nab-paclitaxel (including a total amount of 28 mg of dexamethasone per cycle); Pembro= 4 cycles of monotherapy with pembrolizumab; Pembro/Lenva= 10 cycles of pembrolizumab and lenvatinib; ADOC= three cycles of cisplatin, doxorubicin, vincristine and cyclophosphamide (with a total dosis of 36 mg of dexamethasone per cycle).