Benign masses: Macroscopic and microscopic evaluation

Key points

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Cardiac tumors in adults are rare and most of them are benign.
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The benign cardiac tumors include cardiac myxoma, fibroma, rhabdomyoma, papillary fibroelastoma, hemangioma, lipoma, hamartoma, teratoma, and paraganglioma/pheochromocytoma. By far, the most frequent benign neoplasm in the adult population consists of cardiac myxoma.

Cardiac neoplasms are rare in infants and children and most of them are benign and primary. Rhabdomyoma is the most common primary cardiac neoplasm in children. The second most common tumor of the heart in this age group is cardiac fibroma .

Benign cardiac tumors

Cardiac tumors are rare and about 90% of primary cardiac tumors are benign. Cardiac myxomas are the most common benign primary cardiac tumors in adults . The other benign tumors include rhabdomyoma, fibroma, papillary fibroelastoma, hemangioma, pericardial cyst, benign fatty tumors (lipoma and lipomatous hypertrophy of the interatrial septum), hamartoma, teratoma, and benign neural neoplasm (paraganglioma/pheochromocytoma, neurofibroma, and schwannoma) . Pediatric cardiac tumors are extremely rare; they are categorized into primary and secondary (or metastatic). Primary cardiac tumors are more common, and most of them are benign. Rhabdomyoma is the most common primary cardiac neoplasm in children. The second most common tumor of the heart in children after rhabdomyoma is cardiac fibroma (see Tables 17.1 and 17.2 ) .

Table 17.1

Tumor-like lesion (reactive cardiac masses, pseudotumors, and ectopias).

Tumor-like lesion	Description
Intramural thrombus	Gross: Atrial appendage and ventricular endocardium are common sites for mural thrombi. Most of them occur with underlying heart disease. Atrial thrombi most occur in mitral valvular disease and atrial fibrillation. Ventricular thrombi particularly occur in ischemic heart disease or cardiomyopathy (see Fig. 17.3 A) .
Intramural thrombus	Histopathology: Histopathology reveals layers of fibrin containing some leukocytes and erythrocytes. Fibrosis, proliferation of endothelial cells, and recanalization at the different phases of thrombus formation were seen. It is useful to evaluate the underlying myocardium to make a specific diagnosis (see Fig. 17.3 B) .
Cardiac calcified amorphous tumor (CAT)	Gross: Cardiac calcified amorphous tumor (CAT) is a recently described nontumoral lesion with a clinical demonstration, undistinguishable from other heart tumors such as myxomas. Of great importance is the fact that cardiac masses potentially cause obstruction or embolization and prove fatal. Such masses were formerly called “pseudotumors,” and a majority of them were termed thrombi (see Fig. 17.4 A) .
Cardiac calcified amorphous tumor (CAT)	Histopathology: The lesion revealed multiple calcium deposits within a dense fibrocollagenous background; nevertheless, no malignant cells are seen. Other causes of calcification include myxomas, which present as mobile masses in the heart and could become calcified in about 20% of cases in the left atrium. Fibromas may also have a calcified appearance; nonetheless, they are usually located in the left ventricle with an intramyocardial location. Last but not least, vegetations, echinococcal cysts, tuberculomas, and calcified thrombi are to be borne in mind (see Fig. 17.4 B) .
Ectopic thyroid tissue	Gross : It is defined that thyroid tissue is not located in its normal anatomical position. Intracardiac is a rare finding and common location is right ventricle. Paracardiac location with attachment to the ascending aorta has also been reported .
Ectopic thyroid tissue	Histopathology: Histologically, composed of colloid filled follicles with flat cuboidal cells and uniformly small nuclei resembling normal thyroid tissue (see Fig. 17.5 ) .
Cardiac Tuberculoma	Gross: Pericardial involvement is relatively common; however, myocardial tuberculosis has been reported in not more than 0.3% of all tuberculosis patients postmortem. Tuberculoma shows a well-circumscribed, solid, and creamy egg-shaped appearance with a lobulated surface. It is found in all cardiac chambers, most commonly in the right atrium. Most cases are solitary .
Cardiac Tuberculoma	Histopathology: The histopathological study shows multiple well-formed granulomas with multinucleated giant cells and extensive caseous necrosis compatible with a tuberculoma; however, the Ziehl-Neelsen stain helps reveal the acid-fast bacilli (see Fig. 17.6 ) .
Hydatid cyst	Gross: Hydatid cyst of the heart is uncommon. Any part of the heart may be affected but the most common location is the free wall of left ventricle. Single to multiple cysts with varying size were seen. In general the cysts were soft and filled with clear to slightly turbid fluid (see Fig. 17.7 A) .
Hydatid cyst	Histopathology : The cyst consists of three layers: (1) outer fibrous layer, (2) middle hyaline and acellular laminated layer, and (3) inner germinative layer which consists of daughter cysts and brood capsules with scolices (see Fig. 17.7 B) .
Foregut Cyst	Gross The cyst is predominantly unilocular with a thin fibrotic wall and contains homogeneous gelatinous material. Grossly, it consists of soft and creamy-gray fragments. The average size is about 3–4 cm .
Foregut Cyst	Histopathology It is usual to see ciliated columnar epithelium and foci of squamous metaplasia. Other endodermal and mesodermal elements may exist. The wall may contain hyaline cartilage, smooth muscle, bronchial glands, and nerve trunks (see Fig. 17.8 ) .

Table 17.2

Benign cardiac tumors.

Tumor type	Description
Cardiac myxoma	Gross: Most frequently seen in the left atrium near fossa ovalis but it may occur in any cardiac chamber. Myxoma is usually pedunculated with a short stalk or may be sessile. Consistency varies from a soft, gelatinous, papillary mass to a firm, smooth tumor. The cut surface shows a variegated appearance, frequently with areas of hemorrhage and cyst formation. Calcification may be focal or extensive (see Fig. 17.9 ) .
Cardiac myxoma	Histopathology: The tumor is composed of polygonal, bipolar, or stellate myxoma or lepidic cells that have round to oval nuclei with inconspicuous nucleoli, eosinophilic cytoplasm, and indistinct borders. Cells may be scattered singly, aggregate in small nests or cords, or form rings surrounding vascular channels. Minimal pleomorphism and mitoses are seen. Background typically consists of myxoid and loose fibrous tissue with scattered lymphocytic and histiocytic infiltrate, especially hemosiderin-laden macrophages. Surface thrombus may be identified. Rarely, ossification and mucinous glands may be seen (see Fig. 17.10 ) .
Cardiac Fibroma	Gross : Cardiac fibroma is a firm, white mass which appears circumscribed . They have a whorled cut surface (see Fig. 17.11 ) . It may occur anywhere in the heart but usually involves the ventricles with a predilection for the ventricular septum . Calcification is common (see Fig. 17.12 C). Cardiac fibromas are classically single, but multifocal tumors have been reported .
Cardiac Fibroma	Histopathology: These tumors show bland spindle cells with fibroblastic cytologic features in a collagenous background, with variable numbers of elastic fibers (see Fig. 17.12 A and B). The margins of the tumor are histologically infiltrative and more cellular in infants and children (see Fig. 17.12 D) .
Rhabdomyoma	Gross: This tumor constitutes 50 to 90% of primary heart tumors in children and is usually noted in infancy. Valve obstruction or protrusion into heart chambers may occur. They are well-circumscribed, small but firm, gray-white masses. The size is 3–4 cm or may reach up to 10 cm (see Fig. 17.13 A) .
Rhabdomyoma	Histopathology: The large rounded polygonal cells which are clear (due to dissolution of glycogen during the H and E staining) are known as spider cells. The cytoplasmic vacuoles are separated by strands of cytoplasm extending between cell membrane and nucleus but no mitotic activity is seen. In adults, rhabdomyomas are more cellular with fewer spider cells and more cellular proliferation (see Fig. 17.13 B) .
Hemangioma	Gross: Most hemangiomas are small, endocardial nodules ranging from 0.2 to 3.5 cm in diameter, either polypoid or sessile, and without evidence of infiltration (see Fig. 17.14 A). The most frequent locations are the anterior wall of the right ventricle, the lateral wall of the left ventricle, and the interventricular septum, and sometimes the right ventricular outflow tract is involved .
Hemangioma	Histopathology: Composed of variably sized blood vessels containing bland endothelial cells. They are histologically classified as capillary (small capillary-like vessels), cavernous (large cystically dilated vessels with thin walls), and intramuscular cardiac hemangioma (heterogeneous vessel types) . The capillary type tends to be circumscribed whereas the cavernous and intramuscular types tend to be infiltrative (see Fig. 17.14 B and C) .
Papillary fibroelastoma	Gross: Arborizing, thin strands of tan-white tissue, usually arising from a common stalk. The papillary fibroelastoma has been compared to a “sea anemone,” an appearance heightened by placing the specimen in a bowl of water (see Fig. 17.15 A). Generally they are around 1.0 cm in diameter, but range in size from 0.2 to 7 cm . Their most common location is the aortic valve, followed by the mitral and tricuspid valves, pulmonary valve, and endocardial surfaces .
Papillary fibroelastoma	Histopathology Avascular papillary fronds lined by endothelial cells. The papillary cores contain a proteoglycan-rich stroma, and layers of elastic fibers and collagen are prominent near the base of the lesion. It may show hydropic change (see Fig. 17.15 B and C) .
Lipomatous hypertrophy	Gross: Lipomatous hypertrophy consists of an unencapsulated accumulation of mature adipose tissue within the interatrial septum. Fossa ovalis is generally spared, giving it a characteristic “dumbbell” shape. The atrial septum may measure between 2 cm and 8 cm in thickness (see Fig. 17.16 A) .
Lipomatous hypertrophy	Histopathology: It has a distinctive histological appearance marked by the presence of abundant multivacuolated lipocytes and hypertrophied myocytes (see Fig. 17.16 B) .