Inflammatory Myofibroblastic Tumor: A rare cause of solitary pulmonary nodule (SPN)

A 22-year-old female presented with cough for 1 week with 3 episodes of self-limited hemoptysis. No history of fever, weight loss, dyspnea.

Chest radiograph revealed a well-defined rounded opacity in left lower zone (Fig.1). Subsequently, the patient underwent a contrast-enhanced CT of chest, which revealed a mildly enhancing, well-circumscribed solid nodule of size 2 X 1.5 cm with smooth margins in posterior-basal segment of left lower lobe (Figs. 2 and 3). There was no fat density/calcification/cavitation within the nodule. No associated lymphadenopathy/surrounding ground-glass opacity was seen. Subsequently, PET-CT was performed, which demonstrated increase FDG activity in the nodule. (Figs 4 and 5).

Solitary pulmonary nodule (SPN) is defined as a lung nodule which is a rounded or irregular opacity, which may be well or poorly defined, measuring ⩽3 cm in diameter, surrounded by normal lung on radiological imaging [1]. CT has a better efficiency in detection of SPN than radiographs and also provides better evaluation opportunity. [2] Radiologically, SPN is of two types: solid and subsolid. Subsolid nodules may have purely ground-glass attenuation, be partly solid, or have mixed solid and ground-glass attenuation. [3] The differentials for solid and subsolid SPNs include benign as well as malignant causes. [3] The differentials for subsolid SPNs includes infection, inflammation, haemorrhage, and malignancy, specifically lung adenocarcinoma. [3] The evaluation of SPNs is vital because they may be an early manifestation of lung malignancy. [3] Inflammatory Myofibroblastic tumours (IMTs) are a rare group of neoplasms composed of a mixture of spindle-shaped myofibroblasts or fibroblasts with a variable number of inflammatory cells. [4] IMT can occur in almost any organ, however, lungs and orbits are most frequently affected. [4] Different aetiologies have been proposed for IMT, including chronic infections, autoimmune diseases and trauma; however, scarce information is available about the natural history. Rarely an aggressive behaviour with metastases is seen.[4] IMT represents 0.7% of all lung tumours in general population. Common complaints includes non-specific respiratory symptoms, like cough, chest pain, haemoptysis and non-specific inflammatory symptoms such as fever, malaise and weight loss. On imaging, it appears as a well-circumscribed solitary peripheral lung mass, with predominance for the lower lobes. Calcification is not very common (about 15 %). On CECT, it presents as a soft tissue mass with variable degree of enhancement. [4] Because of their similar radiological appearance to malignant lung masses, biopsy is necessary to confirm the diagnosis. The treatment of choice is surgery and it usually achieves cure. [4]  We performed CT guided biopsy for the histopathological confirmation which revealed, neoplastic spindle cells intricately admixed with inflammatory cells without atypia.(Fig.6) Surgical resection was performed afterwards to achieve the cure.

SPN is a common finding of routine radiology practice, and when encountered, should be carefully evaluated considering possibilities of both malignant and benign causes, including IMT.

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