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Notes: A 66-year-old man with a past medical history of hypertension and arthritis was hospitalized and treated for bacterial pneumonia. Chest X-ray revealed a left-sided chest mass. Computed tomography (CT) scan of the chest demonstrated a large heterogeneously enhancing mass occupying most of the left lower lobe and extending to the inferior aspect of the hilum. It measured 16.6 × 12 cm and caused a mild shift of the mediastinum to the right. The patient declined further work-up or surgical resection of the mass. Dermatologic examination was unremarkable at that time.Over the next 5 months, numerous skin lesions erupted on the patient's trunk. He then experienced several syncopal episodes, at which time he was found to be profoundly hypoglycemic. It was suspected that the chest tumor was producing high serum levels of insulin-like growth factor (IGF) resulting in hypoglycemia and syncope. Serum laboratory investigations were significant for glucose of 20 mg/dL (normal, 60–120 mg/dL), IGF-1 of 39 ng/mL (normal, 152–494 ng/mL), IGF-2 of 927 ng/mL (normal, 210–750 ng/mL), and insulin of 〈 5.0 microunits (MCU)/mL (normal, 0–30 MCU/mL). Surgical extirpation of the chest tumor was recommended.The dermatology service was consulted to evaluate whether the numerous skin lesions in the area of planned surgery would pose an increased risk of infection. Cutaneous examination revealed a dense aggregation of pigmented hyperkeratotic plaques with a “stuck-on” appearance, predominantly localized on the trunk. Many were unusually large or darkly pigmented. A particularly dense distribution was apparent on the left side of the chest (〈link href="#f1"〉Fig. 1a). Numerous large acrochordons were evident on the lower eyelids and in the axillary vaults. Acanthosis nigricans was not present. A biopsy specimen from a hyperkeratotic lesion on the left upper back revealed an acanthotic, hyperpigmented epidermis with a lamellar horn, anastomosing rete, and pseudohorn cysts (〈link href="#f1"〉Fig. 1b).〈figure xml:id="f1"〉1〈mediaResource alt="image" href="urn:x-wiley:00119059:IJD1970:IJD_1970_f1"/〉(a) Dense aggregation of pigmented hyperkeratotic papules and plaques with a “stuck-on” appearance predominantly localized on the left side of the trunk. Many are unusually large or darkly pigmented. (b) Photomicrograph of a biopsy specimen from a hyperkeratotic lesion on the left upper back. An acanthotic, hyperpigmented epidermis with a lamellar horn, anastomosing rete, and pseudohorn cysts is demonstrated (hematoxylin and eosin stain; original magnification, × 4)Left thoracotomy and left lower lobectomy were performed, and surgeons extirpated an 18 × 17 × 10 cm cystic, multilobular, hard tumor (〈link href="#f2"〉Fig. 2a) adhering to the left diaphragm, left lower lobe, and left parietal pleura. Pathologic examination revealed a highly cellular spindle cell tumor (〈link href="#f2"〉Fig. 2b). The nuclei were relatively monotonous with few mitoses. No areas of necrosis were identified. These pathologic findings were diagnostic for solitary fibrous tumor of the pleura.〈figure xml:id="f2"〉2〈mediaResource alt="image" href="urn:x-wiley:00119059:IJD1970:IJD_1970_f2"/〉(a) Gross specimen of solitary fibrous tumor of the pleura measuring 18 × 17 × 10 cm. The mass was a cystic, multilobular, hard tumor adhering to the left diaphragm, left lower lobe, and left parietal pleura. (b) Histopathology demonstrates a highly cellular spindle cell tumor. The nuclei are relatively monotonous with few mitoses. Necrosis is not present (hematoxylin and eosin stain; original magnification, × 20)After surgery, the patient experienced no further syncopal episodes. The truncal seborrheic keratoses decreased substantially in number, size, and density over the following 6 months. Post-operative laboratory data revealed normalization of the blood glucose, insulin, IGF-1 (191 ng/mL; normal, 71–290 ng/mL), and IGF-2 (515 ng/mL; normal, 358–854 ng/mL).