In 1952, Christopherson reported 12 cases of malignant soft tissue tumors with cells of unknown origin arranged in an alveolar or organoid pattern, referred to as alveolar soft fleshy tumors.

bubble_chart Pathological Changes

1. Gross appearance: The lesion is well-circumscribed and may have a capsule. The cut surface is grayish-white, possibly accompanied by necrosis and hemorrhage.

2. Microscopic appearance: Tumor cells are arranged in acinar or organoid structures, separated by thin-walled slit-like blood vessels, resembling the architecture of endocrine organs. The acinar tumor cell nests are round or oval, varying greatly in size, and typically composed of 5 to 50 or more tumor cells.

bubble_chart Clinical Manifestations

It commonly occurs in adolescence and is more frequently seen in females, often located in the deep muscles or fascial membranes of the limbs, with a few cases found in the abdominal wall, perianal area, tongue, retroperitoneum, or the back of the neck. The tumor grows slowly, is painless in the early stages, and is often discovered incidentally. Larger tumors can reach diameters of 6–10 cm. Although the tumor does not grow rapidly, it is highly vascular. Superficial tumors may exhibit palpable pulsations, including those that metastasize to the subcutaneous tissue, where even small tumors of 1 cm in diameter can show significant pulsations. Some patients may develop extensive hematogenous metastases, primarily to the lungs, bones, brain, and subcutaneous tissues, with rare lymphatic metastases. Bone metastases typically present as well-defined osteolytic lesions along the long axis of the bone, without periosteal reaction, resembling certain metastatic bone cancers.

In principle, wide resection of the tumor should be performed, as marginal resection is highly prone to recurrence, with literature reporting recurrence rates as high as 70%. This tumor is insensitive to current chemotherapy and radiotherapy, and the efficacy is uncertain. Therefore, patients must undergo regular follow-up examinations after surgery. Comprehensive check-ups are essential to achieve early detection and early surgery for recurrence and metastasis, enabling patients to survive long-term and continue working. The author once treated a patient who had undergone resection of a primary follicular tumor in the soft tissue of the lower leg at another hospital. Two years later, metastasis occurred in the ipsilateral tibia, requiring tumor resection and fibular grafting. Upon admission to the author’s hospital, local recurrence and bilateral lung metastases were observed. Over four years of treatment, the patient underwent 19 surgeries of varying scales, including four thoracotomies for lung metastasis resection and subcutaneous muscle metastasis resection. Ultimately, the patient succumbed to thoracolumbar metastasis-induced paraplegia, urinary tract infection, renal failure, and widespread systemic metastases. This patient faced financial difficulties and sought treatment only when recurrence or metastasis became unbearable. Had early detection and treatment been possible, the outcome would undoubtedly have been better. Over 14 years, the patient remained in generally good condition for more than nine years and was able to work. This case serves as a relatively typical illustration of the tumor’s biological characteristics.

Differential diagnosis and alveolar rhabdomyosarcoma: the cells are smaller with darker nuclear staining, resembling lymphoblasts. In rhabdomyosarcoma, some rhabdomyoblasts with more reddish cytoplasm or elongated strap-shaped cells can be observed, and there is an absence of sinusoidal vascular networks between the alveoli.

This tumor can be misdiagnosed as adenocarcinoma. The differences lie in the fact that the latter has more regular inner margins of glandular lumens, more tightly arranged cancer cells, may display a certain polarity, and often contains secretions within the glandular lumens.