Aggressive angiomyxoma (AAM) is a rare mesenchymal neoplasm of fibroblastic/myofibroblastic origin with a predilection for the deep soft tissue of pelvis and perineal regions in reproductive women, originally proposed as a separate histopathological entity by Steeper and Rosai in 1983.1 To date, fewer than 150 cases have been reported in the literature.2 AAM is a slow growing tumour, but often problematic due to frequent local recurrences.1 2 However, unusual cases in which the tumour had features consistent with AAM and occurred in head and neck region have been reported.3 4 We report here what is believed to be the first case of AAM originating from lung.

CASE REPORT

A 70-year-old woman was referred to Chonnam National University Hwasun Hospital because of an incidentally detected pulmonary mass on chest radiography. She had been previously well, with no noteworthy medical history.

Physical examination including gynaecological examination was unremarkable. Laboratory findings were within normal limits. Chest CT revealed a well-defined 6.0×5.5 cm sized mass that occupied the right middle lobe (fig 1). Preoperative needle biopsy showed stellate- to spindle-shaped tumour cells in a background of loosely myxoid stroma. Tumour resection by means of thoracoscopic surgery was performed under the impression of benign spindle cell neoplasm. At operation field, the mass was connected to the medial portion of right middle lobe with a narrow stalk. It showed soft to rubbery consistency and glistening external surface with loose adhesion at the entire pleural space. Cystic degeneration with watery content was also found.

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Figure 1 Chest CT revealing a well-defined 6.0×5.5 cm mass in the right middle lobe of the lung.

Microscopically, the tumour was composed of scattered oval- to spindle-shaped cells and variably sized, thin- or thick-walled vessels in a myxoid stroma. The cellularity was generally low to moderate; however, increased cellularity was focally observed around the medium-sized vessels. Vessels often showed perivascular hyalinisation and medial hypertrophy. Cellular atypism or mitotic figures were not noted. Microcystic changes were occasionally detected. In the peripheral portion of the tumour, bronchioles and alveoli were found. In immunohistochemical analysis, the tumour cells showed positive immunoreactivity for vimentin, desmin, actin, oestrogen receptor and progesterone receptor. The cells were negative for cytokeratin, S-100 protein, CD34, bcl-2 and neurofilament (fig 2). Histological and immunohistochemical features of the tumour were consistent with those of AAM.

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Figure 2 (A) The tumour is hypocellular and has thick-walled vessels with hyalinisation. (B) An entrapped bronchiole is present and alveoli are attached to the peripheral portion of the tumour. (C) Oval- to spindle-shaped cells are distributed in the myxoid stoma of the tumour. (D) Microcystic changes are occasionally presented in the tumour. (E) Increased cellularity is occasionally observed around the vessels, but cellular atypia or mitotic figures are not identified. The tumour cells show immunoreactivity for desmin (F), oestrogen receptor (G), and progesterone receptor (H).

The patient was followed up for 8 months postoperatively and remained free of apparent tumour recurrence.

DISCUSSION

To our knowledge, this is the first case of AAM primarily originated from the lung. There are two case reports of metastasised AAM to lung in the literature. One is reported in a 63-year-old woman with pulmonary and mediastinal metastatic AAM.5 The other is reported in a woman of reproductive age, with multiple local recurrences and metastases to the lung.6 Physical and gynaecological examination in the patient of our case was unremarkable. Thus, we believe that the tumour was primarily originated from the lung. However, because the tumour shows locally infiltrative nature or often local recurrence, careful follow-up should be requested.

For AAM, complete wide surgical excision is the treatment of choice.2 AAM usually expresses both oestrogen and progesterone receptors, and its volume is increased during pregnancy.7 This suggests the hormone-dependent nature of the neoplasm. In a recent publication, it has been described that a recurrent AAM of vulva responded to gonadotrophin-releasing hormone agonist medication, and showed complete resolution radiographically.8 Therefore, it is possible that conservative medication may offer a therapeutic alternative to surgery, particularly when operation is impossible. However, identification of novel factors that trigger the growth of the tumour may expand the field of AAM therapy.

For the lung, myxoid or fibrous tumours with numerous vasculature are not frequent. On a histopathological basis, differential diagnoses include solitary fibrous tumour (SFT), myxoid neurofibroma, and low-grade myxoid malignant fibrous histiocytoma. SFT usually arises in the pleura and peritoneum. The arrangement of tumour cells in SFT varies from area to area. Slender spindle- and stellate-shaped tumour cells may resemble the histopathological picture of AAM. However, features of SFT, including abundant hyalinisation, haemangiopericytoma mimicking vascular pattern, and diffuse immunoreactivity to CD34 and bcl-2, are not found in AAM.9 Myxoid neurofibroma is composed of cells with wavy or buckled nuclei, and reveals diffuse immunoreactivity for S-100 protein. The lesion lacks the characteristic vascularity of AAM.10 Low-grade myxoid malignant fibrous histiocytoma tends to show greater pleomorphism, cytological atypia and mitotic activity than AAM. In addition, it reveals a complex and delicate vascular pattern with a network of curvilinear branching capillaries.1

In summary, the clinical and histological features of the tumour reported here were consistent with those of AAM. Here, we report the first case of AAM originated in the lung. Together with our case, accumulation of the cases that occur in unusual sites may lead to knowledge of how AAM may develop outside the pelvic–perineal region.