These are tumours in which muscular tissue is the essential constituent, but just as all muscles have supporting connective tissue so have these, some more, some less. As there are two kinds of muscle, so are there two forms of muscular tumour, those composed of striated, and of smooth muscle respectively.

The Myoma strio-cellulare or Rhabdomyoma is very rare. Tumours of this structure are probably always congenital. They have been seen in the heart, kidneys, ovaries, and testicles. The tumour is not usually composed of ordinary striated muscle, but the muscular fibre is embryonic in character, consisting of spindle-shaped cells, which are transversely striated. Tumours of this kind have strong analogies with sarcomas, and are sometimes designated myo-sarcomas. Besides this, similar rudimentary muscle is occasionally met with in other forms of sarcoma, in cystic tumours of the ovary and testicle, and in teratomas.

The Myoma lsevi-cellulare or Leiomyoma is an exceedingly common form of tumour, and is met with in almost every part where smooth muscle exists normally. According to the amount and density of the interstitial connective tissue is the consistence of the myoma - it may be very dense, and warrant the name Fibro-myoma, or it may be so hard as to resemble cartilage.

Section of a myoma of the uterus stained with carmine.

Fig. 80. - Section of a myoma of the uterus stained with carmine. The muscular nuclei are seen in longitudinal and transverse section, x 350.

Myomas are often described as fibrous tumours, and in appearance they justify this designation. To the naked eye they appear fibrous on section, and even under the microscope they show a fibrous appearance. On adding acetic acid to a microscopic section, or on staining with carmine or other agent, the fibres are seen to be much more abundantly nucleated than ordinary connective tissue. In fact, rod-shaped nuclei (not spindles as in connective tissue) .are so closely set as at once to suggest a cellular tissue (see Fig. 80). It may here be remarked that in the unimpregnated uterus there is the same difficulty in distinguishing the individual spindle-cells. In both cases, however, the cells may be isolated by macerating the tissue for twenty-four hours in a 20 per cent, solution of nitric acid, or for twenty to thirty minutes in a 34 per cent, solution of caustic potash. This makes the tissue rotten, and separates the cells, which are recognized as spindles (as in Fig. 81).

Myomas always arise where muscle already exists, and as smooth muscle is most frequent in the walls of mucous canals and cavities, it is there that they usually originate. The tumour may be continuous with the muscular wall, forming an outgrowth from it, or it may be distinctly isolated and encapsuled. It may remain in the substance of the muscular wall (intraparietal or intramural), or it may slip inwards so as to bulge under the mucous membrane (submucous), or it may pass outwards and present under the serous coat (subserous). In the two latter cases the tumours often become polypoid.

By far the most frequent seat of the myoma is the female organs of generation, generally the uterus, but also the ligaments and ovaries. The so-called uterine fibroids are myomas, and the most important of these are the submucous which so frequently become polypoid, and give rise to haemorrhage, sloughing, etc. The gland-spaces and cysts sometimes found in uterine myomas are regarded by Recklinghausen and others as remains of the Wolffian body.

In the prostate the hypertrophy frequently met with in old men is really from the formation of muscular tissue, and the third lobe which forms a bulging projection at the neck of the bladder is an outgrowth from the muscle of the prostate. Sometimes there are even isolated muscular tumours in the midst of the prostate. This form of tumour is to be distinguished from the glandular tumour, which is a much rarer form of hypertrophy and occurs mostly in young men. Myomas of the oesophagus, stomach, and intestine are somewhat infrequent, and are usually submucous. They have also been seen in the urinary bladder.

Myomas of the skin and subcutaneous tissue occupy a peculiar position. We have first obvious myomas growing usually in parts rich in muscle, such as the nipple and scrotum. We have further multiple myomas of the skin, forming well-defined tumours which are sometimes very painful. Lastly, there is the so-called Tubercula dolorosa, which, at least in most cases, is a myoma, if not in all. It merits a special description.

Muscular fibre cells from a myoma isolated by steeping in nitric acid, x 350.

Fig. 81. - Muscular fibre cells from a myoma isolated by steeping in nitric acid, x 350.

The painful subcutaneous tubercle, Tubercula dolorosa, or Wood's tumour, is, in most cases at least, a subcutaneous myoma. It occurs in the form of a small round tumour under the skin (see Fig. 82), and is commonly the seat of intense pain. The pain indicates some connection with the nerves, but there is no demonstrable nerve fibre to be traced into the tumour. According to Virchow there are tumours of various structure in this category, myomas, angiomas, neuromas. Axmann has suggested, with some probability, that the little tumour may in some cases be an enlarged Pacinian body. Recently Hoggan has described one which he believes to be an adenoma of the sweat-glands, but which Virchow rather takes to be an. angioma. In the cases from which our figures are taken (see Figures 82 and 83), the tumours consisted of a dense interlacing network of fibres, very suggestive of a myoma. On macerating portions in nitric acid the tissue broke up into large spindle cells, as shown in Fig. 83. These tumours are probably myomas of the skin, and several others examined by the author had a similar structure. The view that these tumours are myomas is confirmed, not only by several further observations by the author, but by those of Malherbe, who, in five consecutive cases, found the structure to be uniformly that of the myoma. This author believes that whilst other tumours of the skin may be painful, yet that the myoma has a place and symptomatology of its own, and constitutes the true Tubercula dolorosa.

Tubercula dolorosa.

Fig. 82. - Tubercula dolorosa. The epidermis and cutis are seen in section. The round tumour is situated in the subcutaneous fat. x 8.

Portion of tubercula dolorosa after maceration in nitric acid.

Fig. 83. - Portion of tubercula dolorosa after maceration in nitric acid. The largo spindles are smooth muscle cells, x 350.

The muscular tissue of the tumour probably arises from the arrec-tores pilae of the skin. The tumour tends like other myomas to slip from its original position and to pass into the loose subcutaneous tissue.

From a myoma, a portion of which has become calcified.

Fig. 84. - From a myoma, a portion of which has become calcified. a, muscular fibre-cells impregnated with lime salts; b, a blood-vessel with wall incrusted. x 350.

It may be this shifting of position, by causing dragging on the sensitive nerve twigs of the skin, which leads to the paroxysms of pain.

The myoma is of slow growth. It may go on as long as thirty or forty years, and may reach a very great weight, as much as 60 lbs.

It is nearly always an innocent tumour, but a case is recorded by Brodowski in which a large myoma of the stomach gave rise to secondary tumours in the liver. Retrograde changes may occur, such as fatty degeneration, resulting in shrinking or the formation of cysts. If induration occurs from formation of hard connective tissue, this may calcify, leaving the muscular tissue in the spaces between the calcified trabecular In some cases, from derangements of the circulation in large tumours, we may have an actual necrosis of a portion of the muscular substance, resulting sometimes in absorption and the formation of a cyst. In other cases, the dead structures become calcified, as in Fig. 84, where muscular elements, connective tissue, and walls of blood-vessels were all found impregnated with lime. As the myomas so readily become polypoid, they are liable to be insufficiently nourished, as the neck gets thinner; sloughing may even occur, especially if they present on a mucous surface, and become exposed to injury. Such tumours are also liable to bleed, especially as the vessels in them sometimes undergo great dilatation.

Literature

A considerable number of isolated cases of Rhabdomyoma are recorded. A list of these is given by Kolessnikow in Virch. Arch., lxviii., 554, and by Hubek and Bostrom, D. Arch. f. klin. Med., xxiii., 208; see also Cohkheim, Virch. Arch., lxvi.; Marchand, do., lxxiii. and c. (in last-mentioned paper, Glycogen found in muscle). Bland Sutton, Tumours, 1893. Leiomyoma - Virchow, Ge-schwiilste, iii.; Judassohn (Multiple Myomas of skin), Virch. Arch., cxxi., 1890. Brodowski (Myoma of stomach), Virch. Arch., lxvii., 187(5. Recklinghausen, Die Adenomyome und Cystadenome, 1896. Tubercula dolorosa - Wood, Edin. Med. and Surg. .Jour., 1812; Virchow, Geschwulste, iii., 236; 'Hoggan and Virchow, Virch. Arch., lxxxii., 1880; Malherbe, Congres International, Copenhague, 1884, i., 117.