A3-03 An Endobronchial Secret Beneath the Skin: A Case of Interstitial Granulomatous Dermatitis Revealing a Pulmonary Inflammatory Myofibroblastic Tumor

Introduction

Inflammatory myofibroblastic tumor (IMT) constitutes 0.04 to 1% of all lung neoplasms, and endobronchial presentations are exceedingly uncommon.[1] We report a case in which a skin rash served as the sentinel sign of an occult endobronchial IMT.

Case presentation

A 58-year-old female was referred for evaluation of an incidental lung nodule. She initially presented with a diffuse erythematous rash. Skin biopsy revealed interstitial granulomatous dermatitis (IGD), a histologic pattern often associated with various systemic diseases. Workup to investigate potential underlying causes revealed a hypermetabolic endobronchial lesion (Figure 1). A subsequent flexible bronchoscopy demonstrated yellow nodular material occluding the anterior segment bronchus of the right upper lobe (RUL). An initial forceps biopsy resulted in fragmentation of necrotic tissue, which was successfully retrieved using a cryoprobe, revealing a patent distal airway (Figure 2). Histopathology confirmed an IMT harboring ALK gene rearrangement (Figure 3). Within the necrotic debris, rare acid-fast bacilli were observed, and bronchoalveolar lavage culture later grew Mycobacterium avium complex (MAC). A video-assisted thoracoscopic surgery (VATS) RUL lobectomy was performed, and final surgical pathology showed no residual tumor with negative bronchial margins and negative nodal involvement. At her four-week follow-up, she was free of any respiratory or dermatologic symptoms, and a structured five-year imaging surveillance plan was established.

Discussion

This case presents an intriguing clinical cascade. The pathophysiology we propose is a sequential, domino-like effect. The primary event was the development of an obstructive endobronchial IMT, impairing mucus clearance and creating a localized breeding environment for the second event-colonization and infection with MAC, an opportunistic pathogen known to exploit structural airway abnormalities.[2] Similar postobstructive nontuberculosis mycobacterial infections have been reported in association with endobronchial carcinoid and chondromatous tumors.[3-5] The subsequent systemic inflammatory response provides the most plausible trigger for the patient’s IGD, a subtype of reactive granulomatous dermatitis that can reflect remote immune activation and has been previously linked to MAC infection.[6] This case exemplifies an “endobronchial secret beneath the skin,” in which a concealed pulmonary neoplasm may have caused dermatologic manifestations through a sequence of tumor formation, obstruction, infection, and remote immune activation. The diagnostic process unfolded in reverse, beginning with a skin eruption that ultimately led to the unraveling of a rare endobronchial IMT. This case underscores the imperative of a multidisciplinary, system-wide approach when evaluating a nonspecific “umbrella diagnosis”. It also reminds clinicians of the sentinel role of the skin. Sometimes the surface tells the story first.

This abstract is funded by: None